Aircraft structure



Aug. 8, 1933. G. HQPEGRAM AIRCRAFT STRUCTURE Filed Aug. 2l, 1929Patented Aug. 8, 1933 UNITED STATES PATENT orrlcr:

AIRCRAFT STRUCTURE George H. Pegram, South Orange, N. J.

Application August 21, 1929.\ Serial No. 387,286 .17 Claims. (Cl.244-14) This invention relates to aircrafts and with be subject to arelatively long run and likewise for any given wing structure there is acertain limiting speed necessary to maintain the requisite lift duringflight. Accordingly it'v is one of the principal objects of theinvention to provide an airplane, hydroplane, or the like with meanswhereby the length of run required for the take-olf or landing ismaterially reduced.

Another object ofthe invention is to provide means Wherebyan airplane,hydroplane, or the like may be flown at a much lower speed than ispractical with' existing structures thus enabling the machine to be usedadvantageously for reconnoitering work, aerial photography,

etc.

A feature of the invention resides -in a propeller structure foraircraft whereby the rotation of the propeller directly accomplisheslifting in a substantial part.

Another feature of the invention relates to the means for materiallycontrolling the lift independently of the forward speed of theaircraft;-

Another `feature relates to an aircraft stmoture wherein the lift may hevaried within wide limits without unduly prejudicing the stability ofthe machine in flight.

A further feature of the invention relates to the provision of astructure adapted to have the Aairstreams from the propeller operate torelieve the pressure on the top of the Wings and in conjunctiontherewith to increase the pressure of the bottom of theA wings.

Another feature of the invention is the provision of a propellerstructure adapted to exert a positive lift on the airplanein such a waythat the lifting eiort can be changed to an upward, forward, or downwardeffort by varying the resultant eiort of two or more independentlyoperable propellers.

A further feature of the invention also resides in the arrangement andorganization of elements which go to make up an eiilcient and readilycontrolled aircraft.

The invention, as disclosed, is capable of application to all kinds ofpropelled aircraft and is particularly useful and advantageous asapplied to a hydroplane structure inasmuch as hydroplanes are requiredto alight and take-off Within relatively short distances, particularlyon rough waters. While, therefore, the invention, as hereinafterdisclosed, is applied to an airplane not of the hydroplane type it isnevertheless to be understood that the invention as disclosed is readilyadaptable to such use in a hydroplane and, therefore, the invention isnot to be limited to the particular adaptation shown.

This invention relates .to the combination, construction, arrangement,and relative location of parts, all as will be more fully indicatedhereinafter.

Accordingly there is shown in Fig. 1 a side elevational-view` of anaircraft incorporating the invention;

-liig. 2 is a plan'view of the machine of Fig. l; 75

and

Fig. 3 is a front view in elevation of the construction of the machineof Fig. l.

Fig. 4 shows a modification of the structure of 30 Figs. 31,2, 3.

Similar reference characters lrefer to similar parts throughout the`several views of the drawing.

insofar as the present invention goes, the

ailerons, elevators, rudders, tail skid, etc., are similar to those incommon use adapted, however, to the special feature of the designhereinafter set'forth. The wings l and 2, except as to the manner oftheir support, are of the usual construction. However lthe shapes andrelative association of wings will depend upon the construction andrelative size and position of the engines, except that it will probablybe found that a crescentshape vwill generally he preferable as the shapeof the lower wing. As shown in Fig. 2 the crescent shape is thatcorresponding to the intersection of two circular arcs, it is apparent,however, that other curves than. circular arcs might he used to give acres'- l cent shape which curves will also yield `favorable results.

A special feature of the design is the use of longitudinal trusses whichare adapted to make rigid connection with the fuselage 5. By theadoption of this 'type of construction the wings and fuselage arepreserved in relative position under all variations of stresses to whichthe parts of the airplane may be subjected.

As shown in Figs. l, 2 and 3 the supporting n.10

lcross brace structure 5.

structure or framework of the aircraft is made up of an upper wing 1, alower wing 2, joined by the longitudinal truss 3, and held together bythe front cross brace structure 4, and a rear These longitudinal trussesare disposed at acute angles to the horizontal axis of the plane and arerigidly connected to both the wings and to the fuselage directly orthrough the medium of trusses. i

Observing Fig. 1 it will be seen that the upper wing is placed at asufficient elevation above the lower wing and staggered back of it sothat the stream flow of the propellers is permitted to actmost'eifectively on the surfaces of the Wings. Mounted upon the fuselage6, are' the upper engine 7 and lower engine 8. As shown in Fig. 1 theengines are preferably mounted with the axes of their propeller shaftsapproximately at right angles to each other. It is, of course, apparentthat instead of such mounting, one engine might be mounted' upon thefuselage and two other engines-one on either sidemight be mounted uponthe framework of the airplane to accomplish the same result. When theupper engine is operative the associated propeller draws air from thetops of both wings, thus lessening the pressure thereon. Because of theshape of the lower -wing the air is discharged in such a direction thatit comes below both wings and thus increases the pressure upon theirbottom surfaces, all of these actions tending to lift the aircraft. Onthe other hand, when the lower engine is in action it causes air to bedrawn from the top of the lower wing, thus lessening the pressure uponit and discharges such air against the bottom of the upper wing, thusincreasing the pressure on that surface, all ofthis also tending to liftthe airplane. When only one propeller is operating the entire liftingeffort is in the direction of its line of thrust. However, when bothpropellers are operating at the same time the direction of the resultantforce will lie somewhere between the two propeller shaft axes and can.line of said resultant force will naturally be the line of the axis ofthe engine which vis operating. In order that changes in the quantity offuel may not seriously disturb the equilibrium of the craft, it ispreferred to mount the fuel tank 11 within the fuselage, at or near thecenter of gravity of the entire structure.

It will be observed in Fig. 1 that when the air plane is resting uponthe ground the axis of the upper engine is nearly at right angles withthe ground but with a slight forward inclination and in this positionalmost the entire turning effort of the upper propeller tends to liftthe machine at the same time that it gives to the machine a forwardimpulse. Whereas -some forward motion is always necessary in` order toenable an airplane to be controlled it has been found that in thestructure, as shown, that this would be largely supplied by the lowerengine at slow speed. Inasmuch as the disposition of the propellers andengines, as hereinsure on the upper surface on both Wings and vhorizontal.

increase it on the bottom of said wings it is apparent that the aircraft described will require a comparatively short run in taking-off andin landing. It is further apparent that the machine will not require thesame speed to be maintained for lift while in the air as is requiredwith machines that depend entirely upon the forward motion of theairplane 'for their lifting effort. It is also apparent that the wingsof this structure, as disclosed, may be made shorter than in existingdesigns so that the maximum effects of the engine on the wing may besecured by way of operative wing pressures. It has also been found thatby locating the wheels 10 of the carriage structure 9 approximately'under the longitudinal trusses that a maximum regidity of structure isattained..

It is apparent that in the invention as disclosed the angle of thrustmay be varied through a vertical angle with respect to a horizontal axisof the machine. The invention also renders it practical to make thepropellers sufficiently large in area to lift a given machine withoutany great forward motion of the plane. Also in the invention asdisclosed the lifting effect due to forward motion is combined with avery large lifting effect due to the direct action of the propellers inadjusting the pressures on the bottoms and tops of the wings. It willalso be seen from the disclosure heretofore had that the lifting effect,as disclosed, is caused by either one of the two propellers whenoperating alone, and still more so when both are operating at the sametime. Such lifting of the machine will be helped by the wings and thelocation of the engines with respect thereto both before the aircrafthas any forward motion at all and also after such forward motion hasbegun. After such forward motion has begun the lifting effort of thewings is an increased lifting effort. At the beginning of the forwardmotion the large angle of incidence of the wings while the machine is onthe ground provides a greater lifting effort for the initial slowmotion. Later when the machine attens out as it leaves the ground, theangle of incidence lessens to correspond with the increased speed offorward motion, and the relative speed of the propellers is changed tobring the line of thrust more nearly It is, however, apparent that inall directions of the resultant line of thrust the desired effect uponthe wings, namely that of reducing the pressure on the top andincreasing the pressure on the bottom, is secured. It is apparent toothat when the resultant line of thrust is at an angle with thehorizontal there is exerteda corresponding direct lift on the aircraft,and this lift may be increased by variation in the angle of thrustcaused by varying the speed of either one or both the propellers. As aresult of this method of lifting it is clear that the aircraft iscapable of alighting and taking off with a considerably less run than isnecessary where the line .of thrust is parallel to the axis of the craftand, furthermore, because of the means for progressively varying itsline of thrust the lift may be regulated in accordance with specialconditions without substantially changing the balance or equilibrium ofthe craft. If desired, the usual camber may be given to the wings inorder to increase the ylift of the plane, as is well known. beforedlsclosed, operates to decrease the pres- 'i While the specic structureand arrangement thereof have vbeen disclosed it is to be understood thatthe broad aspect of the invention is capable of application to votherstructures with equal advantages and effects.. Thus, while the engineaxes are shown as mounted in such a position that they are almost at a90 angle with respect to each other, it will be understood that suchaxes. may be so arranged that they make an angle other than 90 withrespect to each other. Similarly, while the crescent shaped lower wingis shown as being a product of the intersection of two circular arcs,still it will'be understood that arcs other than those of the circlemight be used to attain the desired crescent. Although the rudders andfuselage, undercarriage structure, and truss structure shown .may beAci? a specific type, still it will be understood that it is possible tovary these elements along lines well known in the art.

Other changes and modications will be apparent to those skilled in theVart and, therefore, I do not limit myself to a greater extent than iscalled for by the language contained in the following claims, wherein itis intended to cover all the generic andspeciiic features of theinvention herein described. It is further intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense. A

Instead of varying the resultant line of thrust of the propellers byvarying the speed of the associated motors, a single motor may beemployed for both propellers and connected to the motor shaft throughsuitable gearing. A schematic representation of such-an arrangement asshown in Fig. 4 wherein the two' prcpellers i2- and i3 have theirshafts' connected through suitable gearing to a common drive shaft i4.By suitable mechanism not shown the shaft i4. itself maybe rotated aboutits own` anis whereby both propeller structures are moved bodily as aunit so that their resultant line of `-im: t may be varied. If desiredthe meter Yfor driving the propellers of Fig. 4 may 'be mounted on theshaft l-t to turn therewith and may be properly counter-balancedmechanically. It be obvious that in the embodi- .ment of Fig. 4. asingle propeller may be empioyed, it desired, by u: a: about shaft is..

t I claini as new and useful and cdesire to secure byu United Statespatent is:

il.. In Aan air-crat machine, an upper wing end a iower wing ofcontinuous crescent shape rigidly connectm by longitul trusses land heldin staggered reiation aiong the longitul anis of the machine, propellerstructures, and mesnsior v the resultant thrust of the propsllers.A

2. In an air-craft structure, a fuselage hetween two non-overlapstaggeredrwings one ci .saidwings havinga convex forward e and a concaverear edge, and longitudinal trusses interconnecting the said wings andholding them in rigid spaced relation.

3. In an air-craft structure, an upper wing and a lower wingoicontinuous crescent .shape having its concave edge facing rearwardly ofthe machine, said wingsbeing staggered along theiongitai axis of themachine in nonoveriapping relation.

e. In an air-craft structure, an upper wing .and a lower one of saidwings having curved forward and rear edges and interconnected bylongitudinal misses holding said and its line of thrust varied wings inpredetermined l,spaced relationship, and an undercan'lage disposedbeneath'and directly'supporting said longitudinal trusses.

5. In an air-craft structure, an upper wing, and a lower wing rigidlyinterconnected by longitudinal trusses, a fuselage supportedtherebetween, an .undercarriage mounted beneath said lower wing directlyunder said longitudinal trusses, two propellers located with theirshafts approximately at an angle of 90, means for operating onepropeller to create a vacuum on the top of the upper wing and a pressureupon the bottom of the upper wing, and means forV operating the otherpropeller to create a suction on top of the lower wing and a. pressureupon the bottom of the upper wing.

6. In an air-craft structure, means comprising cross braces incombination with longitudinal trusses substantially as described tosupport an upper wing and a lower crescent shaped wing longitudinallyand transversely, said wings being staggered along the longitudinal axisof the machine in non-overlapping relation. 7. In an air-craft structurehaving an upper and a lower wing, one of said wings having a convexforward edge and a concave rear edge, two propellers so located andsupported on the fuselage, that the lines of thrust of said propellerslmake a vertical angle with each other and yield a resultant thrustwhich has a. component of forward impulse.

8. In an air-craft structure of the type dehaving an upper wing and alower wing of crescent shape, the concave head of which opensrearwardly, and undercarriage structure engines mounted so thatpropeller shafts thereof form an angle of approximately 909, saidengines providing a resultant line of thrust which lies between the axesof the shaft of the propellers, and effective when operating to decreasethe pressure upon the upper surfaces. of the wings and increase thepressure upon the lower surfaces of said wings.

9. En an aircraft structure, the combination ci a pair of wings atdierent levels and oset with respectto each other along the longitudinelaxis of the machine, and means between said wings forcreating a suctionon the tcp face of each wing, and simultaneously a pressure on thebottom face of each wing, the last mentioned means including a pair ofpropellers and means for varying the resultant line of 'resultant lineof thrust of said propeller.

` ll. In an aircraft machine, means for varying the line of thrust ofthe machine with relation to an axis of the machine, comprising a pairof non-overlapped wings staggered along the longitudinal axis of themachine, and a pair of propellers with their axes at a iixed angle'mounted beneath said lower wings, longitudinal axis of the structure,and means for mounting' and rotating said propellers so that onepropeller creates a suction on the upper surface of one wing and apressure on the lower surface of said one wing.

14. In an aircraft structure a plurality of propellers, means to varyeach or both propeller speeds to vary the resultant thrust, upper andlower wings staggered along the longitudinal axis of the structure,means for mounting said propellers so that during rotation one propellercreates a suction on the upper surface of one wing and a pressure on thelower surface of said one wing.

15. In an aircraft structure vhaving a. plurality of propellers mountedat an angle to each other to give a resultant line of thrust whichtend's to lift the aircraft with a short run and permits of a. short runmounting and cooperating upper and lower wing structures staggered alongthe longitudinal axis of the structure, and means for mounting androtating said propellers so that each propeller creates a suction on theupper surface of both wings, one of said propellers creating a pressureon the lower surface of both wings.

16. In an aircraft structure havingan upper wing and a lower wing, 'anda plurality of propellers rotatably mounted on axes at an angle 'Vtoeach other and positioned between the planes of said wings so that onepropeller upon operation reduces the pressure upon the tops of bothwings and increases thev pressure on the bottom of both wings, the otherof said propellers reducing the pressure on the top of the lower wingand increasing the pressure on the bottom of the upper Wing,independently of the forward motion of the machine.

17. In an aircraft structure an upper wing, a

lower wing of continuous crescent like shape, longitudinal trussesrigidly connecting said upper and said lower Wing to hold said Wings instaggered non-overlapping relation, and a pair of independentlyrotatable propellers mounted between said wings.

GEORGE H. PEGRAM.

